This invention relates to light duty dishwashing detergents, and in particular, to light duty dishwashing detergents that are effective over a wide range of water hardness levels. Light duty liquid detergents, such as are suitable for use in the washing of dishes, are well known and have met with a high degree of consumer acceptance because of their good washing and foaming properties and convenient form for use. Most of the formulations in commercial use at the present time are based on synthetic organic detergents which, together with supplementing materials often used, give them satisfactory detergency and foaming properties. Nevertheless, there is an ongoing effort to make products that clean and foam even better and produce more stable foams.
A particular problem with generally available detergents exists when the water used for washing is soft (i.e., has a hardness level less than 25 ppm as CaCO.sub.3). At these low water hardness levels, the stability of the foam can be inadequate. Consequently, a need exists for a dishwashing detergent that provides good foam stability over a wide range of water hardness levels.
Surprisingly, it has been found that a dishwashing detergent that is effective and provides stable foam over a wide range of water hardness levels can be prepared by combining, in a three component mixture, an amido amine oxide, an anionic surfactant, and a nonionic surfactant. The use of the amido amine oxide provides an unexpected increase in detergency and foam stability over a range of water hardness levels especially when compared to a detergent formulated with the same anionic and nonionic surfactant without the amido amine oxide. Surprisingly, a detergent containing the amido amine oxide shows a marked increase in performance as the water hardness level is increased when compared to detergents containing an alkyl amine oxide combined with an anionic and nonionic surfactant.
Another problem with generally available detergents exists when the water used for washing has a hardness level greater than about 300 ppm (as CaCO.sub.3). At a high hardness level the amount of foam produced and the performance of the detergent is reduced.
Unexpectedly, it has been found that a dishwashing detergent that is effective at high hardness levels can be prepared by combining, in a three component mixture, an alkyl ethoxylated carboxylate, an anionic surfactant, and a nonionic surfactant. A composition containing the alkyl ethoxylated carboxylate shows a surprising increase in detergency when used in hard water (greater than 300 ppm as CaCO.sub.3) as compared to the detergency of a composition without the alkyl ethoxylated carboxylate.
The present invention thus provides a detergent that exhibits good detergency performance and foam stability over a range of water hardness levels and a detergent that exhibits good detergency and foam stability at high hardness levels.